A MICROTUBULE ASSOCIATED PROTEIN is required for division plane orientation during 3D-differential growth within a tissue

Abstract Communication between tissues and cell division orientation are essential for organ development. During lateral root formation in Arabidopsis thaliana, three-dimensional differential growth is established within a tissue of interconnected and pressurized cells. To emerge, the new organ needs to overcome the mechanical constraints provided by the overlying tissues. How the division plane orientation within the growing organ encountering mechanical constrains is coordinated remains unclear. Here, we show that MICROTUBULE ASSOCIATED PROTEIN 70-2 contributes to this integration of mechanical feedback during lateral root development by being associated with division plane orientation during primordium formation. MAP70-2 expression in the lateral root primordium is dynamic, localizing to cell corners and the cortical division zone prior to cytokinesis. Loss of MAP70-2 leads to misoriented cell divisions in the early stage of lateral root development and defective morphogenesis. Here we propose that MAP70-2 integrates biochemical and mechanical cues to establish correct division plane orientation during three-dimensional differential growth to facilitate lateral root organogenesis.